In general, for acoustic pianos, at the time of depressing a key on a keyboard in an acoustic piano, a static load change and an advance withdrawal sensation occurs wherein the advance withdrawal sensation is referred to as the "let-off sensation". An example of an electronic musical instrument keyboard apparatus, wherein the let-off sensation has been simulated, is disclosed in Japanese Laid-Open Patent Publication Number Hei 6-230770.
The apparatus disclosed in Japanese Laid-Open Patent Publication Number Hei 6-230770 includes a key that is supported by one end on the keyboard chassis so that it is free to swing. The apparatus further includes a hammer that is free to swing in accordance with the depressing of the key and a roller that together with being arranged in a position where it is engaged on the locus of the swinging movement of one end of the hammer, is supported by one end of an elastic body so that it is free to swing. The apparatus is configured so that immediately prior to the termination of the depressing process of the key, one end of the hammer is engaged with the roller and the static load that accompanies the key depressing is increased due to the resistance of the elastic body. When the key depressing process is terminated, the engagement between the end of the hammer and the roller is canceled and the static load that accompanies the key depressing is reduced. Thus, the let-off sensation that occurs in an acoustic piano is simulated.
Although the electronic musical instrument keyboard apparatus disclosed in Japanese Laid-Open Patent Publication Number Hei 6-230770 simulates the let-off sensation of the acoustic piano, a problem occurs during the key releasing process. Namely, when the key depressing is terminated and the key returns to its initial non-depressed position, the end of the hammer also engages the roller such that the static load that accompanied the return of the key is increased due to the resistance of the elastic body. This leads to a change in the increase in the static load during the key releasing process. This change can adversely affect the performance.
More specifically, in the case of an acoustic piano, one cannot say that there is no change in the static load when the key depressing is terminated and the key returns to its position prior to depressing, but that static load change is extraordinarily small and does not hinder the performance. However, in the case of the electronic musical instrument keyboard apparatus disclosed in Japanese Laid-Open Patent Publication Number Hei 6-230770, because the roller is supported by a single elastic body, the counter force that is received from the elastic body is equal both at the time of key depressing and when the key returns and, thus, there is also an increase in the static load when the key depressing is terminated and the key returns to its position prior to depressing. In the case of the electronic musical instrument keyboard apparatus disclosed in Japanese Laid-Open Patent Publication Number Hei 6-230770, when it is made so that the static load is reduced when the key depressing is terminated and the key returns to its position prior to depressing, the let-off sensation at the time of key depressing is also reduced such that it is not possible to obtain the let-off sensation of an acoustic piano.
Embodiments of the present invention consider the problems of the technology of the past that have been described above. At least one objective of embodiments of the instant invention is to present an electronic musical instrument keyboard apparatus which, without losing the let-off sensation at the time of key depressing, is made so that the change in the static load when the key depressing is terminated and the key returns to its position prior to depressing is markedly lessened. In this manner, it is possible to obtain a touch sensation that is equal to the touch sensation of an acoustic piano without adversely affecting the performance.
To reduce the change in the static load, in embodiments of the electronic musical instrument keyboard apparatus of the present invention, it is possible to independently adjust both the first counter force to the key which contributes to the change in the static load at the time of key depressing and the second counter force to the key which contributes to the change in the static load at the time that the key depressing is terminated and the key returns to its position prior to depressing. The apparatus is configured so that the adjustment of both the static load for the let-off sensation at the time of key depressing and the static load when the key depressing is terminated and the key returns to its position prior to depressing is independently achieved. In this manner, the let-off sensation is achieved independently at the time of key depressing and when the key depressing is terminated due to the independent adjustment of the static loads during the key depression and key release. As such, the change in the static load when the key depressing is terminated and the key returns to its position prior to depressing is markedly lessened without losing the let-off sensation at the time of key depressing, thereby allowing the attainment of a touch sensation that is equal to the touch sensation of an acoustic piano without adversely affecting the performance.